3 weeks ago I'd have expected a Shankland call up. Unfortunately Hearts, and him, both hit poor form at a bad time.
Then again, as others have said, Scotland has a terrible record of calling up in-form strikers, Jordan Rhodes being the most egregious example.
I do think Shankland is a good option as he is apparently succeeding at playing up top on his own, which has been a criticism of his game in the past.